Patent GB-627206-A (GB)
Title: Improvements in or relating to measuring apparatus
IPC: G01B5/00
Filed: 1945-06-20
Abstract: 627,206. Indicating-apparatus. STEVENS, A. H. (Ingersoll Milling Machine Co.). June 20, 1945, No. 15694. [Class 106 (iv)] [Also in Groups XX and XXII] An apparatus for measuring relative displacement between two members comprises a rotatable drum having two flexible lines wound around its periphery, said drum being fixed to one of said members, each of said lines being, at one end, anchored to said drum and having the other end so fixed with relation to the second member that when relative movement of the members takes place the drum is rotated an amount corresponding to this relative movement. As shown in Fig. 6, the invention is applied to a device for affording a continuous and accurate indication of the displacement of a milling cutter 33 carried by a spindle 34 which rotates inside a quill 35 which is moved by a pinion 38 and guided vertically by a guideway 36 on a housing 37. Mounted adjacent the quill 35 on a stationary machine part is a tubular sheet metal casing 40 within which and at opposite ends of which are mounted two drums 10 and 22 on shafts 46 and 49, Fig. 9, respectively. The shaft 46 is supported in the upper end of a bar 47 and the shaft 49 in the lower end of a member 47a secured to the bar 47 by the cap screws 50. The drums 10 and 22, each comprise a sleeve, Fig. 11 (not shown), having therein a helical groove which receives a coiled spring defining a helical surface in which are wound the steel tapes 14, 15, 23 and 24, respectively, as shown diagrammatically in Fig. 4. The tapes 14 and 15 are at one end anchored to opposite ends of the drum 10, progress towards one another in a helix, leave the drum from opposite sides and at their other ends are anchored to the slides 30 and 21 respectively. Similarly the tapes 23 and 24 are anchored to the drum 22 at one end and to the slides 30 and 21 at their other ends. Each slide 21, 30 comprises rectangular blocks, Fig. 8, mounted on flanged rollers 65, 66, which are guided for vertical movement against faces 61, 62 of channels 58, 59 fixed by screws 60 to opposite sides of the bar 47. The slides 21, 30 have longitudinal slots 69 for the reception of the tapes 14, 15, 23 and 24, which are adjusted to an initial tension serving to keep the slides 21, 30 in engagement with the surfaces 61, 62 and the angles a, b, c and d, Fig. 4, are made equal to each other and to the helix angle of the helix in which the tapes 14, 15, 23 and 24 are wound. The slide 21, Figs. 6 and 8, is carried by a bracket 73 secured to a flat 74 on the quill 35 and projects through an aperture in a dustexcluding steel strip 76 carried in a longitudinal slot in the rear wall of the casing 40. As the quill 35 moves up and down it takes with it the slide 21 which by means of the tapes 14, 15, 23 and 24 and the drum 22 positively rotates the drum 10 which through gearing, specially designed to take up backlash, rotates an indicating mechanism. The indicating mechanism is contained in a casing 45 and comprises a revolution counter visible through apertures 43 in the face of a dial 2 over which a pointer 3 is rotated. The counter affords measurement in inches and tenths thereof and the pointer in thousandths of an inch. A continuous and precise measurement of the movement of the quill is therefore obtained. In another embodiment (not shown), the slide 21 is connected to a slidable rod in the casing 40 which rod is connected to the quill by a bracket outside the casing 40. Instead of a second drum 22 the slides 21, 30 may be interconnected by a flexible line led over two pulleys, Fig. 15 (not shown). In Figs. 16, 17, the invention is embodied in a protractor and measures the angular displacement of a work holder 104 carried by an arm 100 pivoted on a trunnion 101 on a machine frame 103 and adjustable along a slot 105. The drum 10 is rotatably mounted within a housing 107 at the outer end of the arm 100 and is connected to an angle indicating mechanism contained in a housing 108. Helically wound round the drum 10 are two steel tapes 14 and 15 anchored at one of their ends to the drum and at their outer ends at points 16 and 17 on an arcuate guide surface 111 on a support 111a. Movement of the arm 100 will thereby positively rotate the drum 10. The instrument is sealed against the entry of dirt by a flexible tape secured in spaced relationship above the surface 111.